My problem is that the elevation data does not perfectly match the satellite images. For example, on some small coastal zones, the sea actually reaches the top of some cliffs...

So I'was desperately looking for a way to manually correct the GDEM Aster elevation data (geoTIFF format files) for these zones. I tried using different photo editing software (trial versions and free versions) but none of them lets you set signed or unsigned 16 bit values to individual cells. Even though they are perfectly capable of processing 16 bit greyscale images, they only allow you to set 8 bit values (0-255) in their respective color pickers... I tried : Photoshop CS5, Photoline,, Picture window Pro Paint shop pro 10, Gimp 2

So I came across a software called Wilbur (version 1.8), which is very close to what I need.
Since It does apparently not accept geotiff files (.tiff format), I first converted my file to .png with photoshop and loaded it into Wilbur.
I corrected my map with Wilbur and then saved the file back to a .png surface (with another name of course).
When I got back to photoshop to revert it back to 16 bit Tiff, I noticed that the histogram had been compressed to the low and high values of the terrain, thus destroying the original data... In the file there is an island, whose original max height was 320 meters. After being processed with wilbur (where I only flattened false islands in the sea), its height culminated at over 16000 meters !!

What is it that I'm doing wrong ?

For information, I did save the file as png 16 bit surface.

Thank you very much for your help.

Best regards
Axel

DrunkenEwok

11-07-2012, 11:38 AM

Since no one else has responded yet, I'll try to take a swing (and probably miss). I'm fairly comfortable with height map editing - but haven't really delved into DEM files (yet).

My first thought as to the problem is that the conversion chain is causing your distortion. I suspect the most likely culprit ss the conversion from png to geoTIFF in PS. I know Photoshop reads TIF files, but I'm not sure if there's any supplemental information in the geoTIFF format that it wouldn't understand. Basically, when you make the first conversion from geoTIFF to png - PS would just ignore the bits it doesn't understand and take the raw data (which works fine). But when converting back to geoTIFF, it doesn't add back those special bits that make the geoTIFF work, and you're left with a mess of useless data.

As far as resolution - the "easiest" step I can think of is to try converting your geoTIFFs into a more "DEM"-ish format that Wilbur can read natively. I'd start by scanning through the List of Mapping Software (http://www.cartographersguild.com/software-discussion/1407-list-mapping-software.html) thread, or maybe try the slightly more focused Non-commercial Terrain Software List (http://vterrain.org/Packages/NonCom/) on vTerrain. I haven't used it myself (so I don't know if it would be at all helpful), but I think Quantum GIS (http://www.qgis.org/index.php) would have the capabilities you're looking for - there's a good GIS Tutorial (http://www.cartographersguild.com/tutorials-how/17469-%5Baward-winner%5D-some-pointers-using-gis.html) with a focus on QuantumGIS by Hai-Etlik. Another free software program you might try is Bryce (http://www.daz3d.com/products/bryce/bryce-what-is-bryce) - I'm not sure it has the import/export features you're looking for, but it has some similarities with Wilbur (the ability to "paint" on elevation).

Worst case scenario - you can learn some programming language and edit the file directly. I saw your post on StackExchange that this probably isn't your preferred choice - but if you'd be willing to wait a while for me to skill up, I might be able to help you in that regard. If the steps I've suggested above don't work, and you don't have any real time constraints, you could try posting the geoTIFF and I'll see what I can do...

Hope this helps. :)

It's also possible that whatever software you find to do the translation may also be better suited for actual editing needs.

Redrobes

11-07-2012, 02:02 PM

I have PM'ed Waldronate - he is the man than can regarding Wilbur. I think for editing a geoTIFF tho by hand you may need that quantum GIS or QGis app which is free.

waldronate

11-08-2012, 01:19 AM

Wilbur automatically scales the data set to the full dynamic range available in the format. Thus, a 16-bit PNG will span 0 to 65535. Wilbur doesn't have a way to avoid scaling the output when saving a PNG.